A historic ceasefire came into effect in Colombia Monday, ending a 52-year war between the FARC rebels and the government that claimed more than 250,000 lives.

The full ceasefire ordered by President Juan Manuel Santos and the head of the Revolutionary Armed Forces of Colombia (FARC), Timoleon Jimenez, began at midnight (0500 GMT Monday).

"This August 29 a new phase of history begins for Colombia. We silenced the guns. THE WAR WITH THE FARC IS OVER!" Santos wrote on Twitter one minute after midnight.

A message from the official FARC account at the same time was more restrained: "From this moment on the bilateral and definitive ceasefire begins."

In a statement to reporters in Cuba, where peace talks were held, Jimenez said he had ordered all commanders and units "and each one of our combatants to definitively cease fire and hostilities against the Colombian state."

Santos had issued similar orders Thursday to the Colombian military.

The ceasefire is the first in which both sides are committed to a definite end to the fighting.

"The ceasefire is really one more seal on the end of the conflict. It is the test of fire," said Carlos Alfonso Velazquez, a security expert at the University of La Sabana.

The conflict began in 1964 with the launch of the FARC, a Marxist guerrilla group born out of a peasant uprising. It has left 260,000 dead, 45,000 missing and 6.9 million uprooted from their homes.

To end the war with the FARC for good, Colombians must now vote in an October 2 referendum on the peace accord reached in Havana after nearly four years of talks.

Santos said the exact question that will be put to voters in the referendum would be announced "in the coming days."

"We are on the verge of perhaps the most important political decision of our lives," he said in a speech on Saturday.

Opinion polls show Colombians are divided ahead of the referendum.

Santos's top rival, former president Alvaro Uribe, is leading a campaign to vote "no" to the peace deal. He says a special justice system envisaged for crimes committed during the conflict would give FARC fighters impunity.

Opponents question the FARC's commitment to peace.

"I don't think we can believe them," said Felipe Giraldo, a 25-year-old unemployed man in Bogota.

Others have a high personal stake in the vote.

Adelaida Bermudez, 50, hopes it will bring home her daughter, a FARC fighter for the past nine years.

"I hope we'll have peace... so the children come home," she said in Gaitania, in the central region where the FARC was born.

Santos and Jimenez are due to sign the peace agreement sometime between September 20 and 30 -- possibly at the United Nations General Assembly in New York, said Foreign Minister Maria Angela Holguin.

The end of hostilities will be followed by a six-month demobilization process.

Starting Monday, the FARC's estimated 7,500 fighters will head to collection points to surrender their weapons under UN supervision.

Guerrillas who refuse to demobilize and disarm "will be pursued with all the strength of the state forces," Santos told El Espectador newspaper.

Before the demobilization, the FARC will convene its leaders and troops one last time before transforming into "a legal political movement," according to a statement published on Saturday.

The territorial and ideological conflict has drawn in various left- and right-wing armed groups and gangs.

Efforts to launch peace talks with a smaller rebel group, the National Liberation Army (ELN), have yet to bear fruit.

But with the FARC ordering a ceasefire, the conflict appears to be reaching an end.

"We wish to express our clear and definite will for reconciliation," said Jimenez, known by the nom de guerre Timochenko, in Havana.

"Rivalries and resentment must remain in the past. Today more than ever we regret that so much death and pain has been caused by the war. Today more than ever we wish to embrace (the military and police) as compatriots and start to work together for a new Colombia."